This invention relates to the repair of a discrete damaged portion of an article surface, and more particularly in one form, to the repair of a delaminated surface portion of a fiber reinforced composite laminated turbine engine blade.
Certain gas turbine engine blades designed to operate at relatively lower gas turbine engine temperatures, for example temperatures experienced in a fan or front portion of a low pressure compressor, have been manufactured from fiber reinforced laminated composite materials. Such blades and structures have been widely described in the literature, examples of which are U.S. Pat. Nos. 3,883,267xe2x80x94Baudier et al., patented May 13, 1975; and 5,375,978xe2x80x94Evans et al., patented Dec. 27, 1994. Such patents, in some forms, show details of composite laminated blades of a general type to which the repair of the present invention particularly is related.
Design of certain turbine engine components includes assembly of cooperating articles one of which has a relatively softer surface which can be damaged such as by operating vibration or by erosion, abrasion, etc. during operation with a harder surface of the other. Also, damage can occur due to stresses during molding. One example is a fiber reinforced composite laminated gas turbine engine fan blade having a blade root assembled with and carried by a harder metal disk. Operation of the engine can result in such damage to the softer blade root. When such damage includes delamination of composite plies at a surface of a blade, for example a blade root surface, it is economical to repair the surface rather than to replace the entire article.
Procedures that are commonly used to repair articles having a composite structure include application, such as through pressure means of repair material, for example low viscosity adhesive resin, into a damaged area. Then the article is placed and held in a suitable environment until curing of the repair material is completed. Because of air included or entrapped within the damaged portion and/or the repair material during its preparation for example mixing of a resin and a catalyst, such conventional repair is prone to create internal porosity within the repair during subsequent curing. Therefore, improvement of such conventional type of repair method is desirable to repair high speed rotating modem gas turbine engine fiber reinforced composite fan blades.
The present invention, in one form, provides a method for repairing a discrete damaged portion of an article surface comprising applying uncured repair material at the damaged portion and then subjecting the uncured repair material and the discrete damaged portion to a vacuum to remove entrapped air. In another form, the invention includes providing a vacuum tool sized to cover the discrete damaged portion. The vacuum tool comprises an outer wall including an opening there through, a peripheral edge about the opening and shaped to conform generally with a portion of the article surface about the damaged portion, and gas evacuation means to evacuate gas from within the tool. The method includes providing a releasable gas seal for use between the peripheral edge and the article surface, and providing an uncured repair material. In one form, the repair material then is deposited at the damaged portion and the tool is sealed about the damaged portion through the gas seal. In another form, the repair material is disposed after sealing. Gas is evacuated from within the tool through the gas evacuation means to provide a vacuum adequate to remove entrapped air from the repair material and the discrete damaged portion and less than an amount which results in substantial removal of a required volatile component of the repair material. Then the tool and the releasable gas seal are removed from the article surface.
In another form, the present invention provides a vacuum tool comprising the above described outer wall and the gas evacuation means, in combination with a releasable gas seal generally shaped to interface between and release from the peripheral edge and the article surface.